The present invention relates to a method of controlling access to an elevator car, in particular for maintenance and/or inspection.
In order to perform inspection and/or maintenance to an elevator (which will be called maintenance collectively in the following without loss of generality) it is necessary to get access to the single cars of the elevator, in particular to their roof and/or underside.
Conventionally, the maintenance mechanic thereto calls the car to his floor and stops the car by opening the elevator shaft door with a triangular key when the roof of the car is on a level which is accessible from said floor. Vice versa he may stop the car by opening the elevator shaft door when the bottom of the car is on a level which makes it possible to visually inspect the components arranged in the region of the car bottom or to get access to the underside of the car. With respect to FIG. 1 for example the maintenance mechanic 6 may call the elevator car by operating the landing call button on level E4. The moment at which car 5, arriving in response to the call, is halfway between level E3 and subsequent level E4, the mechanic opens the landing door T4 manually with a triangular key. An opened door automatically stops the traveling car so that mechanic 6 gets access to the car roof 7 from door T4. Having finished maintenance, mechanic 6 leaves the car roof and the elevator shaft 1 and closes the door T4, so that the elevator may resume its normal routine. On the other hand, as shown in FIG. 2, the mechanic 6 may call the elevator car to the lowest level E1. By opening door T1 of level E1, he stops the car on a level between E2 and E1 in order to be able to enter into the shaft pit and to get access to the car underside from the bottom of the shaft pit. Having finished maintenance, mechanic 6 leaves the shaft pit 2 and closes the door T1, so that the elevator may resume its normal routine.
However, this conventional method—although quite simple—has some disadvantages. If there is a group of parallel elevators, the maintenance mechanic cannot selectively call the car to be maintained but the elevator group control will send one car out of the group in response to his call according to a predetermined routine (e.g. based on registered calls, distances between cars and calling floor etc.). Thus, the mechanic cannot select a specific car in order to perform maintenance work on a specific elevator of the elevator group.
Furthermore, it is quite difficult to stop the car at the desired position between two floor levels by opening the door manually, in particular when correct coincidence between the car roof or underside and the landing door is required (if, for example, heavy machinery is to be transferred onto the car roof or the like). Thereto, the mechanic must take into account inertia of the car, stopping distance etc.
Yet furthermore, also unauthorized people can adopt the conventional method, i.e., a simple triangular key allows access to the car roof and has been misused frequently for so-called elevator-surfing.
In view of these problems, JP 02 225278 A suggests a cipher signal output means providing cipher signals causing a control to move the elevator car to a stop position of a car so that its roof level coincides with a selected boarding hall level. After opening the landing door, a mechanic then has access to the car roof.
However, this method requires registration of the cipher signal by the control and thus specific means for inputting and for receiving this signal. Moreover, the cipher signal also must indicate the car to be maintained as well as the floor the mechanic wants to get access from. This method implies additional hardware requirements as well as complex signals in order to overcome the problems described above. Therefore this method is complex and expensive.